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ES6 introduced a whole bunch of new features to JavaScript. One of those features is the class keyword. This introduction has been accompanied by a fair amount of concern and criticism.

Here’s the issue: classes in JavaScript aren’t quite the same as classes in other programming languages. In fact, technically, JavaScript doesn’t really have classes at all. But some say that technically isn’t important. If it looks like a duck, and quacks like a duck, shouldn’t we call it a duck even if technically it’s somewhat similar—but not quite the same—species of waterfowl?

The argument for doing this is that classes are so familiar from other programming languages, that having some way of using classes in JavaScript—even if it isn’t technically the same as in other languages—brings a lot of benefit for people moving over to JavaScript from other programming languages.

But that comes with a side-effect. Anyone learning about classes in JavaScript will basically be told “here’s how classes work …but don’t look too closely.”

Now if you believe that outcomes matter more than understanding, then this is a perfectly acceptable trade-off. After all, we use computers every day without needing to understand the inner workings of every single piece of code under the hood.

It doesn’t sit well with me, though. I think that understanding how something works is important (in most cases). That’s why I favour learning underlying technologies first—HTML, CSS, JavaScript—before reaching for abstractions like frameworks and libraries. If you understand the way things work first, then your choice of framework, library, or any other abstraction is an informed choice.

The most common way that people refer to the new class syntax in JavaScript is to describe it as syntactical sugar. In other words, it doesn’t fundamentally introduce anything new under the hood, but it gives you a shorter, cleaner, nicer way of dealing with objects. It’s an abstraction. But because it’s an abstraction taken from other programming languages that work differently to JavaScript, it’s a bit of fudge. It’s a little white lie. The class keyword in JavaScript will work just fine as long as you don’t try to understand it.

(Full disclosure: Kyle also some very kind things about some of my blog posts at the end of that episode, but you can switch it off before it gets to that bit.)

Both Ashley and Kyle bring a much-needed perspective to the discussion of language design. That perspective is the perspective of a teacher.

In his essay on W3C’s design principles, Bert Bos lists learnability among the fundamental driving forces (closely tied to readability). Learnability and teachability are two sides of the same coin, and I find it valuable to examine any language decisions through that lens. With that mind, introducing a new feature into a language that comes with such low teachability value as to warrant a teacher actively telling a student not to learn how things really work …well, that just doesn’t seem right.